Kidnapping The Devil (Taken! #6 [part 24B])

When a kidnapper calling himself "Jack" kidnaps seven-year-old Samantha Ryan, Jessica and her husband join forces with the FBI to get her back safely.
While Jack is a ruthless killer who has successfully kidnapped children before, he has never abducted anyone like Samantha, who is herself responsible for seven murders.
Complications arise from the start, and when an overzealous FBI agent forces Jack's hand, the coldhearted criminal commits a horrific act that enrages Jessica's husband and sends him on a quest to exact a unique style of vengeance.

This is the second book in The TAKEN! Novel Series.